First appearance on Amazon.com under ASIN B000OCXHWM is on 2007-11-25, with release date of March 3, 2007. This might have been the Mobipocket version - Amazon does not show the ISBN of the ebook.

Publisher does not list ePub version as late as 2012-07-07, but Barnes & Noble site has link using ePub ISBN as early as 2011-07-18. Kobo ebooks lists it as available in ePub format (ISBN not given) as of 2010-07-03. Diesel ebooks does not show ePub on 2009-12-29, suggesting possible release in the first half of 2010.